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"People consider cats to be a member of the family. So he's trying to, quite frankly, take away the civil liberties we all have to choose who we want in our home."

On the Cats To Go website, there's a photoshopped image of a kitten with red eyes and devil's horns.

And on the homepage the words "That little ball of fluff you own is a natural-born killer" are scrawled across a video which says: "Cats are the only true sadists of the animal world" and calls cats serial killers.

"Birds bond for life ... until your cat kills one," one of the slides in the video says.

The video was uploaded to YouTube two years ago by an account called "catsinside" and has received almost 9000 views.

The reasoning given for the campaign is that "cats are incredibly effective hunters and are wiping out our native birds".

"While there are many issues to address, getting one step closer to being a pest-free New Zealand would most certainly be a step in the right direction," the website says.

Dr Morgan did not return Herald calls yesterday.

He has previously spoken out against cats. In a post on his blog in August last year, Dr Morgan said: "Sorry, at the risk of causing a Pussy Riot, that ball of fluff you have at home is as much a predator as stoats, rats and mice. It has to go."

He said that removing predators was a prerequisite for building back the community of our native fauna.

Mr Kerridge said Dr Morgan's logic was "a bit radical, over the top and completely wrong".

He also questioned the validity of the economist's research.

The video says research shows that "if you put a small animal next to an eating cat, it will pause, kill it, then return to its meal". But the 1975 study quoted, as referenced on the website, shows that of 44 subjects, 26 did not attack prey (more than 50 per cent), and many who did kill presented defensive postures.

Mr Kerridge said they knew from SPCA surveys that fewer than half of New Zealand's domestic cats killed other animals. The ones that did caught far more rodents than birds.

"People blindly say, 'Yes, it's cats that kill all the birds'.

"Gareth Morgan is way out of line because very few native birds fall at the hand of cats, domestic cats."

In 2011, the total cat population was 1.419 million and 48 per cent of all households owned at least one cat, according to a survey by the New Zealand Companion Animal Council.